1. Field of the Invention
The present invention relates to an aspherical LED angular lens for central distribution patterns and its LED assembly, and more particularly to an optical lens applied to an LED light emitting source to produce patterns and an LED assembly composed of the optical lens and applied for LED illumination, and a flash light of a cell phone or a camera.
2. Description of the Related Art
Light emitting diode (LED) has many advantages such as low voltage, low power consumption and long life, and thus it has been used extensively in the areas of indicators and illuminators. Since LED features a simple color light, a mini flat package, LED is commonly used as a flash light of a cell phone or a camera. However, the light source emitted from an LED die is not a point light source, and its brightness is non-uniform. Many researchers in the light collection related field have conducted extensive researches on reducing the size of an LED die, improving the light emission efficiency, and using an optical lens, which are the trends of the related technological development.
The design of LED optical lens can be divided into a primary optical lens and a secondary optical lens, and the primary optical lens is a lens packaged directly on an LED die and generally used for concentrating light, and the secondary optical lens is used in an LED or an LED array primarily used for scattering a light beam. In the designs of conventional primary optical lenses including a symmetrical aspherical lens used in ES2157829, a spherical lens used in Japan Pat. Nos. JP3032069, JP2002-111068 and JP2005-203499, U.S. Pat. No. US2006/187653 and China Pat. No. CN101013193, and a spherical lens used in a bulky LED and disclosed by JP2002-221658. The primary optical lens produces a specific distribution pattern such as a large-angle, a small-angle, a circular or an elliptical pattern at an uniform peak intensity for advanced applications and structures a LED array to give an optimal optical effect, in addition to the concentrating of light. In an application of the primary optical lens as shown in FIG. 1, a lens 23 is covered onto an LED die 21, and a silicon gel is filled between the lens 23 and the LED die 21, and the LED die 21 is a die that emits a blue light, and the silicon gel contains yellow phosphors. When the LED die 21 emits the blue light, the blue light goes through the silicon gel and becomes a white light by wavelength conversion. After the lens 23 concentrates the emitted light. The primary optical lens as disclosed in Japan Pat. Nos. JP2004-356512, JP2005-229082, JP2006-072874, JP2007-140524 and JP2007-115708, U.S. Pat. Nos. US2005/162854, US2006/105485, US2006/076568, US2007/114551, US2007/152231, U.S. Pat. Nos. 7,344,902, 7,345,416, and 7,352,011 and TW Pat. No. M332796 adopt the optical lens to produce a distribution pattern; Japan Pat. No. JP60007425, WIPO Pat. No. WO/2007/100837 produces an elliptical distribution pattern; or China Pat. No. 200710118965.0 produces a rectangular, square or bar-shaped pattern smaller than 160°.
As science and technology advanced, electronic products tend to be developed with a light, thin, short and small design and a multiple of functions, and electronic products including digital still cameras, PC cameras, network cameras and cell phones have a camera lens, or even personal digital assistants (PDA) have installed a lens, and an LED flash light or an LED lamp for illuminations for the products of this sort is composed of one or more LED assemblies to form an array. To facilitate the portability and comply with the user-friendly requirement, the LED flash light or the LED lamp for illuminations not only conforms with the luminous flux, but also works together with LED assemblies in different distribution patterns, while achieving a smaller volume and a lower cost. For the requirements of a primary optical lens of an LED, the manufacture of a conventional primary optical lens with a complicated appearance or an optical lens with a diffractive surface has the drawbacks of a high difficulty of the manufacture, an easy deformation of plastic injection molding, a difficult shaping of glass and a high cost. Therefore, users require a design and an assembly of an easy-to-manufacture LED lens with a simple optical surface, such that a central angular circle distribution pattern can be formed by concentrating light by the LED and a peak intensity can be greater than 72° and smaller than 108°, and the luminous flux ratio can be greater than 85%.